Historians have long believed that the remains of the lavish houses and parkland would never be recovered. But this spring, Italy’s Ministry of Cultural Heritage, Cultural Activities and Tourism will open the Nymphaeum Museum of Piazza Vittorio, a subterranean gallery that will showcase a section of the imperial garden that was unearthed during an excavation from 2006 to 2015. The dig, carried out beneath the rubble of a condemned 19th-century apartment complex, yielded gems, coins, ceramics, jewelry, pottery, cameo glass, a theater mask, seeds of plants such as citron, apricot and acacia that had been imported from Asia, and bones of peacocks, deer, lions, bears and ostriches.